EFFECTS OF CHRONIC DIETARY FRUCTOSE WITH AND WITHOUT COPPER SUPPLEMENTATION ON GLYCEMIC CONTROL, ADIPOSITY, INSULIN BINDING TO ADIPOCYTES AND GLOMERULAR-BASEMENT-MEMBRANE THICKNESS IN NORMAL RATS

Sucrose feeding over a long period has been reported to induce glomeru lar basement membrane (GBM) thickening and insulin resistance in norma l rats. These effects are attributed to the fructose moiety of the suc rose molecule, to Cu deprivation or both. Consequently, our aim was to evaluate the long-term effects of fructose feeding with normal or hig h amounts of Cu on body weight, plasma lipids, blood glucose regulatio n, GBM thickening and insulin binding to adipocytes. Four groups of ei ght Sprague-Dawley rats were fed for 10 weeks on a diet containing 570 g carbohydrate/kg supplied either as starch (S), dextrose (D), fructo se (F) or fructose-starch (1:1, w/w; FS), and an adequate amount of Cu (12 mug Cu/g diet). A fifth group was fed on diet F supplemented with 24 mug Cu/g diet (FCu). After 10 weeks the epididymal adipose tissue and kidney weights expressed per 100 g body weight (relative weight) w ere heaviest in the F and FCu groups (P < 0.0001, ANOVA). The GBM thic kness was within the normal range in the five groups but significantly higher in group D (1.95 (SE 0.04) nm and lower in group FS (1.79 (SE 0.02) nm when compared with group S (1.85 (SE 0.03) nm, P < 0.05). Ins ulin binding to adipocytes (expressed per cell) was lowest in the F an d FCu groups, intermediate in groups D and FS and highest in group S ( P < 0.05). Fasting plasma insulin level was higher in group F than in the FCu and FS groups (P < 0.05), whereas fasting plasma glucose, tota l cholesterol and triacylglycerol levels remained within the normal ra nge in all groups. We conclude that in normal rats a 10-week fructose- rich diet with an adequate amount of Cu produced deleterious metabolic effects on adipose tissue, insulin binding to adipocytes, and plasma insulin, but not on GBM thickening even though kidney weight was signi ficantly increased. However, a moderate fructose intake mixed with oth er sugars did not have adverse effects.